Garden Hits & Myths: Exploring the science behind hanging baskets

If I had to choose but one ‘flowery’ item that provides the biggest bang for the loonie, it would be a hanging basket. Whether it’s spilling over with gorgeous flowers or dripping with delicious cherry tomatoes, hanging baskets instantaneously transform a barren spot into a luscious, eye-level oasis.

Jim Hole

Published on: June 2, 2017 | Last Updated: June 3, 2017 6:32 AM MDT

Hanging baskets can be a welcome addition to any yard, but learning the science behind them can help to ensure you get the most out of them during the growing season.Supplied / Nancy Vervynck

But while hanging baskets always look great the moment they are hung, keeping them in great shape can be a challenge for some gardeners. The ‘secret’ to healthy and lush hanging baskets — those that perform beautifully from spring right through until fall — is to understand a bit about the basics of high performance plant growth.

A bit of science

The first thing to understand about plants in hanging baskets — or any plants for that matter — is that there is no substitute for good genes. Great baskets always begin with great plant varieties. Plants without the right genetic formula will never perform well regardless of how much you baby them.

For example, if you try growing a beefsteak tomato variety in a hanging basket, it will be a weedy-looking monster by early summer, simply because it has far too aggressive a growth habit for the restrictive space of a basket. On the other hand, varieties like ‘Tumbler’ or ‘Tumbling Tom’ have a natural mounding growth habit and just the right ‘fruit to foliage’ ratio, making them a perfect match for hanging baskets.

Once you get the genetics right, have a close look at the both the potting soil and soil volume. Potting soils in baskets should have plenty of ‘pore spaces’ to allow for easy root penetration and movement of air and water throughout the mixture. The best quality potting soils contain coarse-fibred sphagnum peat moss, a popped rock called ‘perlite’ lime to adjust the pH into the correct range, and a ‘wetting agent’ that allows easy penetration of water throughout the soil.

I have tested a wide range of potting soils over the years, and many are just too dense for good root growth and have pH levels that are excessively acidic. There is very little that can be done to improve poor quality potting soil once it’s in a basket, so if you choose to blend it yourself, get the best ingredients and incorporate them in the correct proportions.

Now, while soil quality is critical for hanging baskets, so too is volume. Unlike open garden plots, the root zone in hanging baskets is very limited. Therefore, choosing large hanging baskets is very important for optimum plant performance. Simply choosing a 14-inch hanging basket rather than a 12-inch hanging basket will have a dramatic impact on plant growth because of the increased soil volume. In fact, the amount of potting soil in a 14-inch hanging basket is nearly double that of a 12-inch basket. That extra soil volume can mean the difference between a beautiful, season-long hanging basket and one that struggles to survive beyond June.

What should you do?

Once you have hanging baskets hung, there are three very important things that you must do: water, water, water! I can’t begin to tell you the number of dead hanging baskets that I’ve seen simply because they weren’t properly watered.

Now, I am certainly not pointing the finger at anyone, because I’ve killed my fair share of hanging baskets by letting them dry out, but the way I look at it is that if you can remember to give your dog or cat water, keeping your hanging baskets hydrated shouldn’t be extraordinarily difficult. And yes, I do have a dog.

My golden rule for watering a hanging basket is this: Water the basket until the water pours out the drain holes. ‘Baptizing’ the plants — as we call it at the greenhouses — by spraying the foliage will not get an adequate amount of water into the root zone. The best watering strategy is to soak the basket and then check it by sticking your index finger into the soil, up to the first knuckle. If the soil feels moist, don’t water. If it feels dry, soak the potting soil once again.

The last detail is fertilization. In our greenhouses I incorporate a ‘controlled release’ fertilizer into every basket so that the plants have some food even after they leave the premises. But it is still important to fertilize the plants with a liquid fertilizer, like 10-4-3, at least weekly. This will help keep the plants lush right through until autumn.

Growing great hanging baskets is relatively easy if you take care of the basics: genetics, soil, water, and fertilizer. I’ve had many people tell me that they’ve harvested more than 500 cherry tomatoes in a single season from one hanging basket, so I know that they have done a great job of fine-tuning their growing formula.

Doing a bit of math, the fruit — or flowers, as the case may be — in each basket costs a fraction of a penny each. On a loonie-per-loonie basis that’s a lot of bang for your baskets.

Jim Hole is the owner of Hole’s Greenouses in St. Albert and a certified professional horticulturist with the American Society for Horticultural Science.

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